Fixed error in coercion to boolean for legacy versions (#1402)

src/org/mozilla/javascript/NativeArray.java

@@ -665,6 +665,10 @@ public Object getDefaultValue(Class<?> hint) {
             Context cx = Context.getContext();
             if (cx.getLanguageVersion() == Context.VERSION_1_2) return Long.valueOf(length);
         }
+        if (hint == ScriptRuntime.BooleanClass) {
+            Context cx = Context.getContext();
+            if (cx.getLanguageVersion() <= Context.VERSION_1_2 && length == 0) return Boolean.FALSE;
+        }
         return super.getDefaultValue(hint);
     }
 

src/org/mozilla/javascript/ScriptableObject.java

@@ -763,6 +763,9 @@ public Object[] getAllIds() {
      */
     @Override
     public Object getDefaultValue(Class<?> typeHint) {
+        if (typeHint == ScriptRuntime.BooleanClass) {
+            return Boolean.TRUE;
+        }
         return getDefaultValue(this, typeHint);
     }
 

testsrc/org/mozilla/javascript/tests/Issue1402Test.java

@@ -0,0 +1,62 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.javascript.tests;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+import org.mozilla.javascript.Context;
+import org.mozilla.javascript.Scriptable;
+
+public class Issue1402Test {
+    @Test
+    public void codeCanBeRunWithoutRaisingErrorInLegacyMode() {
+        Utils.runWithAllOptimizationLevels(
+                cx -> {
+                    cx.setLanguageVersion(Context.VERSION_1_0);
+
+                    Scriptable scope = cx.initStandardObjects(null);
+                    Object result =
+                            cx.evaluateString(
+                                    scope,
+                                    "var Base = function() {};\n"
+                                            + "var Extending = function() {};\n"
+                                            + "Extending.prototype = Base;\n"
+                                            + "var x = new Extending();\n"
+                                            + "!!x\n",
+                                    "test",
+                                    1,
+                                    null);
+                    assertEquals(true, result);
+                    return null;
+                });
+    }
+
+    @Test
+    public void emptyArraysCoerceToFalseInLegacyMode() {
+        Utils.runWithAllOptimizationLevels(
+                cx -> {
+                    cx.setLanguageVersion(Context.VERSION_1_0);
+
+                    Scriptable scope = cx.initStandardObjects(null);
+                    Object result = cx.evaluateString(scope, "!![]", "test", 1, null);
+                    assertEquals(false, result);
+                    return null;
+                });
+    }
+
+    @Test
+    public void emptyArraysCoerceToFalseInNormalVersions() {
+        Utils.runWithAllOptimizationLevels(
+                cx -> {
+                    cx.setLanguageVersion(Context.VERSION_1_3); // And any above
+
+                    Scriptable scope = cx.initStandardObjects(null);
+                    Object result = cx.evaluateString(scope, "!![]", "test", 1, null);
+                    assertEquals(true, result);
+                    return null;
+                });
+    }
+}